Solvent fractionation of waxcontaining mixtures



July 22, 1952 w. CLARKE 2,604,432

' SOLVENT FRACTIONATION OF WAX-CONTAINING MIXTURES- Original Filed Sept. 16, 1947 2 ""A 00/ T/VE ATTEASYT INVENTOR Patented July 22, 1952 SOLVENT FRACTIONATION OF WAX.-

CONTAINING MIXTURES I Edgar'W. Clarke, Laurel Springs, N. J., assignor to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania.

Original application September 16, 1947, Serial No. 774,230. Divided and this application November 5, 1949, Serial No. 125,722

I 3 Claims. 7 1

The present invention relates to the treatment of oily waxes, and more particularly to the separation of wax-containing mixtures into fractions of higher and lower melting point, using a solvent comprising nitro-benzene and anadditive comprisingBB' dichlordiethyl ether.

Thisapplication is'a division of'copending application. Serial Number 774,230, filed September 16, 1947, now Patent Number 2,578,510, and entitled "Solvent Fractionation of Wax-Containing Mixtures." I

The present inventionis especially applicable to the de-oiling of hydrocarbonwaxes containing not more than about, 70% of oil, and to the separation of wax mixtures of low oil content into fractions of diflerent'melting point. The process of the present invention may be applied in the refining, purification, or separation of wax stocks such as petroleum slack wax, crude microcrystalline wax, paraffin waxes, petrolatum 1wax, montan wax, ceresin, ozokerite, waxes from the destructive r non-destructive hydrogenation of mineral oil, synthetichydrocarbon oil, shale oil, coal, and waxes produced synthetically by the catalytic reaction of hydrocarbons, or waxes derived from the modified Fis'che'r-Tropsch reaction of carbon monoxide and hydrogen. The process of this invention is especially'applicable in'the separation of wax mixtures containing color bodies and oil into a higher melting wax fraction of light color and low oil content, and a lower. melting wax fraction of'darker color and containin most of the oil originally present in the wax mixture.

In accordance with this invention, a wax-containing mixture is separated into fractions of higher and lower melting point by countercurrentl'y contacting the wax-containing mixture, in an extraction zonewith an extraction solvent and a'solvent additive -or additives at a temperature such that two liquid phases are formed, one .comprising the higher melting wax fraction with minor amounts of solvent and additive, and the other comprising th'e lowermelting wax fraction with major amounts of solvent andadditive, separating the liquid phases from one another, and removing the solvent and additive from each. The extraction solvent and additives employed may have a density greater than that of the wax. However, when .the additive or additives are partially immiscible with the extraction solvent and are less dense than such solvent or the wax, the additive or additives will flow countercurrent to the extraction solvent and will appear with that liquid phase comprising thelhigher melting wax fraction. The success 0f the process depends upon the control of the temperature throughout the extraction zone" and'upon'the regulation of the proportions ofsolvent and additive used, and the points of introduction of the wax-containing mixture, the-solvent, and the additive in'to the extraction zone;

-'I'he extraction solvent may be defined as an agent which, when intimately mixed with awaxcontaining mixture, forms two liquid phases or layers, one comprising a rafiinate phase contain: ing mostly'wax of higher melting point than the untreated wax and a-portionof the solvent, and the other comprising an extract phase containing mostly solvent, and wax-of lower melting point than the untreated wax,- as well as a major portion of the color bodies and oil originally present in the untreated wax. 7 v

The solvent additive maybe defined as an agent. used in conjunction with the extraction solvent for the purposeof modifyingthe characteristics. of the extraction solvent. The additive may lower the tem-perature at which solidwax precipitates out of the extraction solvent, or it may raise themiscibility temperature of the extraction solvent with the wax. However, the addi% tive chosen for a particular extraction solvent must not excessively lower the selectivity of the extraction solvent at thetemperature of extrac tion.

The extraction solvent may be-employed in amounts ranging from 1 to 5 volumes of solvent per volume of; untreated wax stock, whilethe additive or additives may. be used in amounts ranging from 0.05 to- 1 volume per volume of untreated wax. V

The extraction solvents which may be employed in accordancewith the present invention com-- prise nitro-benzene containing a small amount of BB dichlordiethyl ether, 7 g

The solvent additive or additives, whichare usually employed in amounts constituting not more than 50% by volume of the extraction-solvent, comprise BB dichlordiethyl ether.

"The process of the present invention-maybe carried out ina multi-stage batch countercurrent extraction system or in a continuous countercurrent extraction system, preferably a tower provided with perforated bafiles or containing a packing material such 'as ceramic'shapes, tiles, metal wool, or 1 fragments ofceramic material, glass,- pumice, carborundum, or concrete; For most effective operation; a temperature gradient is maintained in the system by means of heating or cooling coils or jackets, the temperature increasing in the direction of flow of the raflinate or higher melting waxifraction.

The present invention may be' further under stood with reference to the accompanyingdraw ing Which illustrates diagrammatically a-con'tinz:

uous extraction system suitable for carrying out An extraction solvent comprising:

nitrobenzene containing a small amount of BB dichlordiethyl ether is continuously introduced from vessel 3 by means of valve-controlled pipe 4 and manifold into the upper section of the tower below the raiiinate outlet at a rate of 200 volumes per hour. The first additive com.- prising BB dichlordiethyl ether is continuously introduced from vessel 6 through valve-controlled pipe 1 into the extraction tower [below the wax inlet at a rate of volumes per hour:

The j second additive also comprising BB dichlordiethyl ether-is continuously introduced by valve-controlled pipe 8 into the extraction tower I between the point of introduction of the first additive and theoutlet of the extract phase at a rate of. 10 volumes per hour, such second additive being delivered from vesselsthrough pipe It. An intimate countercurrent contacting of the -wax stock, the extraction solvent, and the additives is effected in tower I, a temperature gradient being maintained in the tower by means of coils I-I' through'w'hich a heating or cooling medium is circulated as required, the temperature adjacent the top of 'the tower being higher than that adjacent the bottom of the tower, the contents of the tower being entirely in the liquid phase. The wax stock, being subjected to the action of the solvent and additives, is caused to separate by solvent action into two fractions,

the higher melting fraction wax passing upwardly through the tower together with a minor amount of dissolved extraction solvent and additive, and being withdrawn therefrom above the level of the dotted line l2 representing the higher melting wax phase relatively free of entrained, immiscible solvent and additive. The raflinate phase comprising the higher melting wax and dissolved solvent and additive is passed from the'top of tower 1 through valve-controlled pipe I3 into a vacuum evaporator or still I4 wherein the solvent and additive is removed from the higher melting wax by vaporization, the solvent and additive vapors passing through pipe l5 into fractionating tower l6 provided with a reboiler or heating coil [1, while the higher melting wax is drawn from the bottom of evaporator IA and delivered by valve-controlled pipe l8 into storage vessel l9. tion was white in color, and had a substantially higher. melting point and a lower oil content than the original waxy mixture.

The extract phase comprising the lower melting wax fraction, color bodies, oil, and the major portion of the extraction solvent and additives is withdrawn from the lower section of tower beneaththe level of the dotted line 28 representing the extract phase relatively free of entrained, higher melting wax. The extract phase is delivered by valve-controlled pipe 2| into a vacuum evaporator or still 22 wherein the solvent and additives .arevaporized from the lower melting wax, the latter being drawn from the bottom of the evaporator and passed by valve-controlled pipe. 2 3 to storage vessel 24. The lower melting wax was brown in color and had a substantially lower'melting point and a higher oil content than the original waxy mixture.

Such wax frac- The solvent and additive vapors are passed from the top of evaporator 22 through pipe 25 into fractionating tower I'GLIWherein such vapors together withthose introduced through pipe iii, are fractionated, the extraction solvent, i. e., n-itrobenzene, being drawn from the bottom of the tower as a liquid and returned by means of pipe 2-6 to the solvent storage vessel 3 for reuse. The desired small amount, for example, 5% to 10% of BB dichlordiethyl ether is incorporated in the nitrobenzene by introducing the BB dichlordiethyl ether from vessel 6 by means of valve-controlled pipe 21. The additive, i. e., BB dichlordiethyl ether, separated from the nitrobenzene by fractionation in tower I6 is taken overhead as vapor by pipe 28, condensed in condenser 29 and returned by pipes 30 and 3! to vessels 6 and 9, respectively. A portion of the vapor stream maybe diverted. throughva-lvecontrolled pipe 32, condensed in condenser 33; and the condensate'returned' as reflux to the top of tower Hi by pipe 3ft, 1

Dependingupon the'temperature of operation, the first additive may "be introduced somewhat above the point of introduction of the liquefied waxy stock, for example, by means of valvecontrolled pipe 35 rather than through valvecontrolled pipe 1, in which case the second additive may be admitted through either or'both of valve-controlled pipes I and 8 below the point of introducttion of the wax stock. In'genera-l, the rafi'inate wax phasewithdrawn from the ex-- traction tower will containfrom 5%110 25% of. solvent and additive, whilethe extract wax phase will contain from to'90% of solvent and additive;

In the event that the extraction is to-be car ried out in a multi-stage batch countercurrent system, for example, a l-stage system using the solvent and additives specifically set forth above; the wax stock would be'introduced into the first stage extractor, the extraction solvent comprising nitrobenzene and a small amount of BB dichlordiethyl ether would be introduced into the fourth stage extractor; and the first ads ditive, i. e., BB dichlordiethyl ether, would be introduced into the first stage extractor. The second additive, e. g., the same ether, would be introduced into the second stage extractor. The extract phase is withdrawn from the first stage extractor, while the r'affinate. phase would be removed from the fourth'stage extractor. The temperature would increase progressively. from the first stage to the'fourth stage, using the waxy stock, solvent, and additives described hereinabove. It is'to be understood, of course,- thatithe' quantities and composition of the solvent and of the additives may be varied within certain limits.

Exemplary of the solvent and additive materials which may be used in accordance .with this invention is the following, the quantities being volumes per unit volume of waxy stock:

Extraction Solvent 1st Additive 2nd Additive BB dichlordiethyl ether 0.1i0.05 vols.

BB ether BB dichlordiethyl ether 0.1 0.05 vols.

Nitrobenzene +10% dichlordiethyl 210.4 vols.

The present invention is further illustratedby v ether.

was extracted in a system similarto that shown in the accompanying drawing, the extraction solvent comprising 2 volumes of nitrobenzene containing of BB dichlordiethyl ether, the first additive comprising 0.1 volume of BB dichlordiethyl ether, and the second additive comprising 0.1 volume of BB dichlordiethyl The slack wax was introduced into tower l by pipe 2, the solvent by pipe 4 and manifold 5, the first additive by pipe land the second additive by pipe 8. The temperature in the extraction tower was maintained constant at 95 F. After countercurrentcontacting and removal of the raflinate phase from the top of the tower, and the extract phase from the bottom of the tower, the solvent and additives were recovered from the wax fractions by vacuum evaporation and fractionation. The results are shown in the following table:

Where the extraction operation is conducted in a tower, it has been found that a tower having a height of about feet and a diameter of 6 feet is satisfactory. The tower is provided with suitable packing to within about 4 feet of the top and bottom thereof, such spaces functioning as quiescent zones in which entrained materials. are permitted to separate from the raffinate and extract phases, respectively. In such a tower, the wax stock is charged at a point about 13 feet from the bottom thereof, or approximately the distance from the bottom of the tower. The extraction solvent is charged just above the upper level of the packing, for example, 3 to 4 feet from the top of the tower. The first additive may be introduced adjacent the point of introduction of the wax stock, for example, 2 feet above or below the wax inlet. The second additive is introduced approximately 2 feet below the point of introduction of the first additive. These values may be altered somewhat, depending upon the tower design, the solvent and additives used, and the temperatures maintained at various levels in the tower. The raffinate phase is withdrawn from the top of the tower, and the extract phase from the bottom thereof, the extraction solvent being more dense than the wax stock.

I claim:

1. The method of separating a wax-containing mixture into fractions of higher and lower melting point, which comprises countercurrently contacting said wax-containing mixture in an extraction zone with an extraction solvent and solvent additives at a temperature such that two immiscible liquid phases are formed, one comprising the higher melting wax fraction containing solvent and additives, and the other comprising solvent and additives and the lower melting wax fraction, separating the phases from one another, and removing the solvent and additives from each, the solvent'being introduced into "the" 'extraction zone near the point of withdrawal of the higher melting wax fraction, the first additive being introduced adjacent the point ofintroduction of the wax-containing mixture, and the second additive being introduced between the point of introduction of the first additive and the point of withdrawal of the lowermelting wax fraction, the solvent comprisingfl'fi to 2.4-volumes of nitro benzene containing a small amount of BB dichlordiethyl ether'per volume'of wax-containing mixture, the first additive comprising 0.05 to 0.15 volumes of BB'dichlordiethyl ether per volume of wax-containing. mixture, and the second additive comprising 0.05 to--0.15 volumesof 'BB' dichlordiethyl ether per volume of wax-containing mixture.

2. The method of separating a wax-containing mixture into fractions of higher and lower melting point, which comprises counter-currently contacting said wax-containing mixture in an extraction zone with an extraction solvent and solvent additives at a temperature such that two immiscible liquid phases are formed, one comprising the higher melting wax fraction with minor amounts of solvent and additives, and the other comprising the lower melting wax fraction with major amounts of solvent and additives, separating the phases from one another, and removing the solvent and additives from each, the solvent being introduced into the extraction zone near the point of withdrawal of the higher melting wax fraction, the first additive being introduced between the point of introduction of the wax-containing mixture and the point of withdrawal of the lower melting wax fraction, and the second additive being introduced between the point of introduction of the first additive and the point of withdrawal of the lower melting wax fraction, the solvent comprising 1.6 to 2.4 volumes of nitrobenzene containing 10% of BB dichlordiethyl ether per volume of wax-containing mix ture, the first additive comprising 0.05 to 0.15 volumes of BB dichlordiethyl ether per volume of Wax-containing mixture, and the second additive comprising 0.05 to 0.15 volumes of BB dichlordiethyl ether per volume of wax-containing mixture.

3. In a method of separating a wax-containing mixture into fractions of higher and lower melting point, wherein the wax-containing mixture is contacted in an extraction zone with an extraction solvent and solvent additives at a temperature above the melting point but below the temperature of complete miscibility of the mixture, the steps which comprise introducing 1 volume of liquefied wax-containing mixture into the extraction zone at a point intermediate the points of withdrawal of the higher and lower melting waxes including the solvent and additive, introducing 1.6 to 2.4 volumes of extraction solvent comprising nitrobenzene containing 10% of BB dichlordiethyl ether at a point adjacent the point of withdrawal of the higher melting wax fraction including solvent and additive, but intermediate said point of withdrawal and the point of introduction of the liquefied wax-containing mixture, and introducing 0.05 to 0.15 volumes of an additive comprising BB dichlordiethyl ether intermediate the point of introduction of the liquefied wax-containing mixture and the point of withdrawal of the lower melting wax fraction including solvent and additive, introducing 0.05 to 0.15 volumes of an additive comprising BB dichlordiethyl ether at a point intermediate the point of Va temperature such that two immiscible liquid phases are formed, one phase comprising the higher melting wax fraction containing minor amounts of solvent and additives, and the other liquid phase comprising the lower melting wax fraction and major amounts of solvent and additives, the temperature in the extraction zone increasing in the direction of flow of the higher melting wax fraction, separately withdrawing the respective liquid phases from the extraction zone, 15

and removing the solvent and additives from each.

EDGAR W. CLARKE.

REFERENCES CITED The following references are of record inthe file of this patent:

UNITED STATES PATENTS '1 Number Name Date 2,017,fl 32 Bahlke "e Oct. 15, 1935 2,063,369 Diggs et a1 Dec. 8, 1936 2,138,833 Brown et a1. Dec. 6, 1938 2,160,930

Whiteley et a1. J une 6, 1939 

1. THE METHOD OF SEPARATING A WAX-CONTAINING MIXTURE INTO FRACTIONS OF HIGHER AND LOWER MELTING POINT, WHICH COMPRISES COUNTERCURRENTLY CONTACTING SAID WAX-CONTAINING MIXTURE IN AN EXTRACTION ZONE WITH AN EXTRACTION SOLVENT AND SOLVENT ADDITIVES AT A TEMPERATURE SUCH THAT TWO IMMISCIBLE LIQUID PHASES ARE FORMED, ONE COMPRISING THE HIGHER MELTING WAX FRACTION CONTAINING SOLVENT AND ADDITIVES, AND THE OTHER COMPRISING SOLVENT AND ADDITIVES AND THE LOWER MELTING WAX FRACTION, SEPARATING THE PHASES FROM ONE ANOTHER, AND REMOVING THE SOLVENT AND ADDITIVES FROM EACH, THE SOLVENT BEING INTRODUCED INTO THE EXTRACTION ZONE NEAR THE POINT OF WITHDRAWAL OF THE HIGHER MELTING WAX FRACTION, THE FIRST ADDITIVE BEING INTRODUCED ADJACENT THE POINT OF INTRODUCTION OF THE WAX-CONTAINING MIXTURE, AND THE SECOND ADDITIVE BEING INTRODUCED BETWEEN THE POINT OF INTRODUCTION OF THE FIRST ADDITIVE AND THE POINT OF WITHDRAWAL OF THE LOWER MELTING WAX FRACTION, THE SOLVENT COMPRISING 1.6 TO 2.4 VOLUMES OF NITROBENZENE CONTAINING A SMALL AMOUNT OF BB'' DICHLORDIETHYL ETHER PER VOLUME OF WAX-CONTAINING MIXTURE, THE FIRST ADDITIVE COMPRISING 0.05 TO 0.15 VOLUMES OF BB'' DICHLORDIETHYL ETHER PER VOLUME OF WAX-CONTAINING MIXTURE, AND THE SECOND ADDITIVE COMPRISING 0.05 TO 0.15 VOLUMES OF BB'' DICHLORDIETHYL ETHER PER VOLUME OF WAX-CONTAINING MIXTURE. 